1. Field of the Invention
The present invention relates to an opening/shutting apparatus for controlling a flow of fluid in a duct, and more particularly to an opening/shutting apparatus for flow control, in which pressure applied to a damper door by fluid when an interior of a duct is hermetically sealed is transmitted to a knob through link and rod, but is directed to a rotational center of the knob, thereby causing the sum of moments acting on the knob to amount to zero.
2. Description of the Related Art
Such an opening/shutting apparatus for flow control refers to one designed to rotate a knob to generate a rotational force, and to cause the rotational force to be transmitted through link and rod to a damper door located in a duct, so that the damper door rotates to open/shut a fluid channel.
In a conventional opening/shutting apparatus for flow control composed of a damper door, a link, a rod and a knob (Korean Patent Publication No. 10-2003-0055383), no means capable of supporting pressure applied to the damper door by fluid when an interior of a duct is hermetically sealed is separately provided. Hence, there is a problem in that the damper door is vibrated or that a sealed effect is deteriorated.
In order to address the foregoing problem, for example, Korean Utility Model Publication No. 20-1998-0038245 has proposed to add a separate means such as a locking step. However, this addition has an influence on operation of the knob to thus prevent the knob from being smoothly operated. In addition, this is responsible for increase in the number of components, which leads to increase of costs as well as unreliability of quality.